Accidentally omitted a detail in OP306

I accidentally forgot to mention in my OP306 that I was fired from a job a few years ago, due to unsatisfactory performance. However, I did mention that detail in the SF85P form. I was sent an email asking for an explanation of why I didn’t mention it in my OP306 form. I was honest as possible ( I am quite scatterbrained), but am scared that they will rescind my offer due to my forgetfulness. What should I do or expect?